In recent years, light bulb-type lamp light sources using a semiconductor light-emitting element such as an LED (Light Emitting Diode) have become a widespread replacement for incandescent light bulbs.
Such lamp light sources typically feature a number of LEDs mounted on a single mounting substrate while a circuit unit for lighting the LEDs is held in the internal space of a case between the back of the mounting substrate and a base. The light produced by the LEDs radiates outward through a globe (see Patent Literature 1).
Also, the case is formed of a metal having thermoconductive properties and thus transmits heat produced by the LEDs to the base. The case is typically made so as not to accumulate heat (see page 12 of Non-Patent Literature 1)